OK I don't want to stir the pot or anything, but not ALL low cost spay/neuter clinics are like that. Only speaking for our area, but the low cost spay/neuter clinics here actually ask local Vets to volunteer for the clinic. The clinic staff ensures that the Vet has a good reputation, and is experienced. Same vet who does the procedure in his office and charges 3xs what the clinic does, is handling the actual procedure in the clinic.
We have one major clinic in our area. It has a 3 month waiting list and is known for its reputation of being great before/during/after the procedure. They not only used skilled vet techs to assist the volunteering vet, but do monitor your pet throughout the operation. The Vet techs call before your appointment to help you prep your animal for the operation, and to tell you what to expect, give you more instruction while you're there dropping off your pet, and than have an emergency vet on standby just in case something happens once you get home that you need to take your pet too (free of charge if its an post-op problem).
Not only that but your pet must be fully awake and alert for 2 hours at least before you can pick up your pet. This is done for continued monitoring post-op.
Typical neuter in our area about $150, clinic charges $35. Main reason they're able to do it so cheaply - Vet is volunteering (no charge), Vet techs are volunteering (no charge), the clinic staff who handles the administration side are volunteering (no charge) and the building they operate in was donated to them, and the equipment was bought by doing MANY MANY fundraisers over a span of 3 years.
I personally think low cost spay/neuter clinics are a terrific service to the community, because lets face it, not everyone who gets a pet thinks about the expense of vetting the pet and they're not able to afford it, this way communities can cut down on unwanted litters of puppies/kittens. The clinic above that I was talking about tells you, if you can pay a traditional vet fee, please do so, so they can help as many people who can't afford the higher cost of the vet's office.
---Getting off soap box now---